This invention relates to the hydroprocessing of petroleum and chemical feedstocks using bulk Group VIII/Group VIB catalysts. Preferred catalysts include those comprised of Nixe2x80x94Moxe2x80x94W.
As the supply of low sulfur, low nitrogen crudes decrease, refineries are processing crudes with greater sulfur and nitrogen contents at the same time that environmental regulations are mandating lower levels of these heteroatoms in products. Consequently, a need exists for increasingly efficient desulfurization and denitrogenation catalysts.
In one approach, a family of compounds, related to hydrotalcites, e.g., ammonium nickel molybdates, has been prepared. Whereas X-ray diffraction analysis has shown that hydrotalcites are composed of layered phases with positively charged sheets and exchangeable anions located in the galleries between the sheets, the related ammonium nickel molybdate phase has molybdate anions in interlayer galleries bonded to nickel oxyhydroxide sheets. See, for example, Levin, D., Soled, S. L., and Ying, J. Y., Crystal Structure of an Ammonium Nickel Molybdate prepared by Chemical Precipitation. Inorganic Chemistry, Vol. 35. No. 14, p. 4191-4197 (1996). The preparation of such materials also has been reported by Teichner and Astier. Appl. Catal. 72, 321-29 (1991); Ann. Chim. Fr. 12, 337-43 (1987), and C. R. Acad. Sci. 304 (II), #11, 563-6 (1987) and Mazzocchia, Solid State Ionics, 63-65 (1993) 731-35.
Now, when molybdenum is partially substituted for by tungsten, an amorphous phase is produced which upon decomposition and, preferably, sulfidation, provides enhanced hydrodenitrogenation (HDN) catalyst activity relative to the unsubstituted (Nixe2x80x94Mo) phase.
In accordance with this invention there is provided a process for hydroprocessing a hydrocarbon feedstock, which process comprises contacting said feedstock, at hydroprocessing conditions, with a bulk catalyst comprised of at least one Group VIII metal and two Group VIB metals, which catalyst comprises a bulk metal catalyst containing non-noble metal Group VIII molybdate in which at least a portion but less than all of the molybdenum is replaced by tungsten. The hydroprocessing process is selected from at least one of hydrodesulfurization, hydrodenitrogenation, hydrodemetallation, hydrodearomatization, hydroisomerization, hydrodewaxing, hydrotreating, hydrofining and hydrocracking.
In a specific embodiment of the invention, there is provided a process for selectively hydroconverting a raffinate produced from solvent refining a lubricating oil feedstock which comprises:
(a) conducting the lubricating oil feedstock to a solvent extraction zone and separating therefrom an aromatics rich extract and a paraffins rich raffinate;
(b) stripping the raffinate of solvent to produce a raffinate feed having a dewaxed oil viscosity index from about 80 to about 105 and a final boiling point of no greater than about 650xc2x0 C.;
(c) passing the rafffinate feed to a first hydroconversion zone and processing the raffinate feed in the presence of a bulk metal catalyst under hydroconversion conditions wherein the bulk metal catalyst comprises a Group VIII non-noble metal molybdate in which at least a portion but less than all of the molybdenum is replaced by tungsten to produce a first hydroconverted raffinate; and
(d) passing the first hydroconverted raffinate to a second reaction zone and conducting cold hydrofinishing of the first hydroconverted raffinate in the presence of a hydrofinishing catalyst under cold hydrofinishing conditions.
In another embodiment, there is provided a process for selectively hydroconverting a raffinate produced from solvent refining a lubricating oil feedstock which comprises:
(a) conducting the lubricating oil feedstock to a solvent extraction zone and separating therefrom an aromatics rich extract and a paraffins rich raffinate;
(b) stripping the raffinate of solvent to produce a raffinate feed having a dewaxed oil viscosity index from about 80 to about 105 and a final boiling point of no greater than about 650xc2x0 C.;
(c) passing the raffinate feed to a first hydroconversion zone and processing the raffinate feed in the presence of a bulk metal catalyst under hydroconversion conditions wherein the bulk metal catalyst comprises a non-noble metal Group VIII molybdate in which at least a portion but less than all of the molybdenum is replaced by tungsten to produce a first hydroconverted raffinate,
(d) passing the hydroconverted raffinate from the first hydroconversion zone to a second hydroconversion zone and processing the hydroconverted raffinate in the presence of a hydroconversion catalyst under hydroconversion conditions to produce a second hydroconverted raffinate;
(e) passing the second hydroconverted raffinate to a hydrofinishing reaction zone and conducting cold hydrofinishing of the second hydroconverted raffinate in the presence of a hydrofinishing catalyst under cold hydrofinishing conditions.
In yet another embodiment there is provided a process for selectively hydroconverting a raffinate produced from solvent refining a lubricating oil feedstock which comprises:
(a) conducting the lubricating oil feedstock to a solvent extraction zone and separating therefrom an aromatics rich extract and a paraffins rich raffinate;
(b) stripping the raffinate of solvent to produce a raffinate feed having a dewaxed oil viscosity index from about 80 to about 105 and a final boiling point of no greater than about 650xc2x0 C.;
(c) passing the raffinate feed to a first hydroconversion zone and processing the raffinate feed in the presence of a hydroconversion catalyst under hydroconversion conditions to produce a first hydroconverted raffinate;
(d) passing the hydroconverted raffinate from the first hydroconversion zone to a second hydroconversion zone and processing the hydroconverted raffinate in the presence of a bulk metal catalyst under hydroconversion conditions wherein the bulk metal catalyst comprises a non-noble metal Group VIII molybdate in which at least a portion but less than all of the molybdenum is replaced by tungsten to produce a second hydroconverted raffinate.
(e) passing the second hydroconverted raffinate to a hydrofinishing reaction zone and conducting cold hydrofinishing of the second hydroconverted raffinate in the presence of a hydrofinishing catalyst under cold hydrofinishing conditions.
In another embodiment of the present invention the catalyst composition is prepared by a process which comprises contacting the Group VIII non-noble metal component with the Group VIB metal components in the presence of a protic liquid wherein during contacting not all of the Group VIB and/or Group VIII non-noble metals are in solution.
The preferred catalyst composition of the present invention can be further described as a bulk mixed metal oxide which is preferably sulfided prior to use, and which is represented by the formula:
(X)b(Mo)c(W)dOz
wherein X is non-noble Group VIII metal, preferably Ni or Co, especially Ni, the molar ratio of b: (c+d) is 0.5/1 to 3/1, preferably 0.75/1 to 1.5/1, more preferably 0.75/1 to 1.25/1;
The molar ratio of c:d is preferably  greater than 0.01/1, more preferably  greater than 0.1/1, still more preferably 1/10 to 10/1, still more preferably 1/3 to 3/1, most preferably substantially equimolar amounts of Mo and W. e.g., 2/3 to 3/2; and z=[2b+6(ctd)]/2.
The essentially amorphous material has a unique X-ray diffraction pattern showing crystalline peaks at d=2.53 Angstroms and d=1.70 Angstroms.
The mixed metal oxide is readily produced by the decomposition of a precursor having the formula:
(NH4)a(X)b(Mo)c(W)dOz
wherein the molar-ratio of a:b is xe2x89xa61.0/1, preferably 0-1; and X, b, c, and d, are as defined above, and z=[a+2b+6(c+d)]/2. The precursor has similar peaks at d=2.53 and 1.70 Angstroms.
Decomposition of the precursor may be effected at elevated temperatures, e.g., temperatures of at least about 300xc2x0 C., preferably about 300-450xc2x0 C., in a suitable atmosphere, e.g., inerts such as nitrogen, argon, or steam, until decomposition is substantially complete, i.e., the ammonium is substantially completely driven off. Substantially complete decomposition can be readily established by thermogravimetric analysis (TGA), i.e., flattening of the weight change curve.